Handheld imaging apparatus for, and method of, imaging targets using a high performance, compact scan engine

ABSTRACT

An apparatus for, and a method of, electro-optically reading a target by image capture, employ a scan engine in a handheld housing having a tilted handle. A single tilted printed circuit board (PCB) in the handle has front and rear surfaces that respectively face toward and away from the target during reading. An optical assembly having a pair of fold mirrors is mounted on the rear surface, for receiving return light from the target through an aperture in the PCB along the horizontal, and for directing the return light along an internal folded optical path. An imaging lens assembly is mounted between the fold mirrors and has an imaging axis that extends generally parallel to the PCB. The imaging lens assembly projects the return light onto a solid-state, two-dimensional, image sensor to enable the return light to be detected over a field of view, and to generate an electrical signal indicative of the detected return light.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of, and claims thebenefit under 35 U.S.C. §119(e) from, U.S. patent application Ser. No.13/584,948, filed Aug. 14, 2012, entitled “High Performance Scan Enginewith Rear-facing Image Sensor in Handheld Arrangement For, and MethodOf, Imaging Targets Using the Scan Engine” (“parent application”), andcontains at least a claim to a claimed invention that has an effectivefiling date as defined in 35 U.S.C. 100(i) that is on or after Mar. 16,2013, the present application being commonly owned with said parentapplication by Symbol Technologies, Inc., the entire contents of saidparent application being incorporated herein by reference thereto.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to a compact scan engine havinga rear-facing image sensor and an apparatus for, and a method of,imaging targets using the compact scan engine and, more particularly, toa high performance, compact, inexpensive, durable, and handheld, areaimaging reader for electro-optically reading symbol targets to bedecoded and/or non-symbol targets or forms to be imaged.

BACKGROUND

Solid-state imaging systems or imaging readers have been used, in bothhandheld and/or hands-free modes of operation, to electro-optically readtargets, such as one- and two-dimensional bar code symbols, each bearingelements, e.g., bars and spaces, of different widths and reflectivities,to be decoded, as well as non-symbol targets or forms, such asdocuments, labels, receipts, signatures, drivers' licenses, employeebadges, and payment/loyalty cards, each bearing alphanumeric characters,to be imaged. A known exemplary imaging reader includes a housing eitherheld by a user and/or supported on a support surface, a front windowsupported by the housing and aimed at the target, and a scan engine orimaging module supported by the housing and having a solid-state imager(or image sensor) with a sensor array of photocells or light sensors(also known as pixels) that lie in an imaging plane and face forwardlytoward the front window, and an imaging lens assembly for capturingreturn light scattered and/or reflected from the target being imagedthrough the window over a field of view, and for projecting the returnlight onto the image sensor along an internal optical path between thewindow and the image sensor, to initiate capture of an image of thetarget over a range of working distances in which the target can beread. The imaging lens assembly includes a plurality of lenses arrangedalong an imaging axis that is generally perpendicular to the imagingplane of the image sensor. Such an image sensor may include a one- ortwo-dimensional charge coupled device (CCD) or a complementary metaloxide semiconductor (CMOS) device and associated circuits for producingand processing electrical signals corresponding to a one- ortwo-dimensional array of pixel data over the field of view. Theseelectrical signals are decoded and/or processed by a programmedmicroprocessor or controller into information related to the targetbeing read, e.g., decoded data indicative of a symbol target, or into apicture of a non-symbol target.

In order to increase the amount of the return light captured by theimage sensor, especially in dimly lit environments and/or at far rangeimaging and reading, the known imaging reader may also have anilluminating light assembly, which also faces forwardly toward the frontwindow, for illuminating the target with illumination light from anilluminating light source, e.g., one or more light emitting diodes(LEDs) and illuminating lenses, for reflection and scattering from thetarget. The known imaging reader may also have an aiming light assembly,which also faces forwardly toward the front window, for projecting anaiming light pattern or mark, such as a “crosshair” pattern, with aiminglight from an aiming light source, e.g., an aiming laser or one or moreLEDs, through aiming lenses on the target prior to imaging. The useraims the aiming pattern on the target to be imaged during an aiming modeprior to imaging and reading.

In the hands-free mode, the user may slide or swipe the target past thewindow in either horizontal and/or vertical and/or diagonal directionsin a “swipe” mode. Alternatively, the user may present the target to anapproximate central region of the window in a “presentation” mode. Thechoice depends on the type of target, operator preference, or on thelayout of a workstation in which the reader is used. In the handheldmode, the user holds the reader in his or her hand at a certain distancefrom the target to be imaged and initially aims the reader at thetarget. The user may first lift the reader from a countertop or asupport stand or cradle. Once reading is completed, the user may returnthe reader to the countertop or to the support stand to resumehands-free operation.

Thus, handheld imaging readers having a two-dimensional imager, alsoknown as area readers, have become increasingly popular in the lastseveral years due to their ability to scan two-dimensional symboltargets, and also to omni-directionally read one-dimensional symboltargets, and also to take pictures of non-symbol targets or forms. Yet,despite these advantages, adoption of area readers still lags behindimaging readers having a one-dimensional imager, also known as linearreaders, as well as laser-based readers, because the area readers costmore and have certain performance issues, such as a smaller workingdistance range.

One factor that limits the working distance range of existing handheldarea readers is pixel resolution of the image sensor. Pixel resolutionrefers to the size of the smallest detail that the image sensor canresolve (assuming focus is adequate) and is determined by the size of adetail in the image projected onto the image sensor. In the case ofreading symbol targets, the image of the symbol target on the imagesensor grows smaller as the distance to the symbol target is increased.When the width of the image of an element (bar or space) in the symboltarget approaches (for instance) around the same size as a pixel, thenthe end of the working distance range has been reached, simply becauseif the symbol target moves any further away than that, then that elementcan no longer be resolved by the image sensor. The pixel resolutionlimits the working distance range, because the internal optical pathdistance between the front window of the reader and the imaging lensassembly is limited by the size of the reader housing, and causes thefield of view to be unnecessarily wide.

Typically, the image sensor is positioned about 2.5 inches back from thefront of the reader housing due to a practical, ergonomic requirement tobuild the reader housing with a size that users have become accustomedto with previous generations of reader technology. Another userexpectation is that the working distance range begins very close to afront end, or nose, of the housing, because many users will naturallyposition the target close-up to the nose when attempting to scan thetarget. In order for a symbol target to be scanned close to the nose,the field of view must be able to expand to be at least about 1.75inches in a horizontal direction across the nose. If the field of viewis much smaller than that, then it may not entirely cover common symboltargets, and such symbol targets will not be read. This requirement,along with the positioning of the image sensor inside the housing,results in a need to make the field of view expand at an angle of around40 degrees horizontally, which is typical of all general purposehandheld area readers that are available at this time.

Sometimes, it is desirable for the reader to scan a target at a distancewell away from the nose, for example, when scanning a heavy or bulkyitem that is too difficult, or inconvenient, to lift out of a shoppingcart onto a check-out counter. Thus, the handheld reader will often becalled upon to read both close-in and far-out targets. With the typicalfield of view angle of about forty degrees, the field of view willdiverge rapidly as the target distance increases, and the pixelresolution will fall off correspondingly. All area readers would benefitif the rate of divergence of the field of view could be reduced, sincethat would mean that the size of the image on the image sensor will notgrow smaller as quickly when the target distance to the target isincreased.

Aside from pixel resolution, another factor that limits the workingdistance range is depth of focus of the imaging lens assembly. When theimaging lens assembly is focused farther away from the image sensor, thedepth of focus is increased. The working distance range may be increasedsimply by focusing the imaging lens assembly farther away from the nose.However, this solution has not been utilized in existing handheldreaders, because it will reduce the sharpness of the image close-up tothe nose, thereby preventing reading of some close-in targets.

Another performance issue with existing area readers relates to parallaxinvolving the aforementioned aiming light assembly. Since the outgoingaiming light cannot coexist with the incoming return light projectedonto the image sensor in the same place, the aiming light sources mustalways be positioned to one side (or above or below) the image sensor.It is desirable that the aiming light be visible close to the center ofthe field of view of the image sensor at a distance away from thereader. The aiming light on existing scanners is therefore directed at aslight angle with respect to an imaging axis of the imaging lensassembly, so as to converge the aiming light on the center of the fieldof view at a convenient distance away from the reader. Unfortunately,this results in the aiming light being off-center at all otherdistances, and the larger the angular difference between the aiminglight assembly and the imaging lens assembly, the faster the aiminglight goes off-center.

As previously mentioned, the known area readers are expensive not onlyin terms of component cost, but also in terms of the labor cost ofassembling and aligning their various components. Unlike linear readersand laser-based readers, optical and ergonomic constraints havecompelled the use of multiple printed circuit boards (PCBs)interconnected by flexible wiring, such as ribbon cables, and connectorsinside the handheld area readers. The image sensor is typically mountedon one of the PCBs, while other components, e.g., the illumination LEDsor the imaging lens assembly, are mounted on another of the PCBs. In anarea reader, the image sensor must be positioned in a planeperpendicular to the imaging axis of the imaging lens assembly. Thisimaging axis projects out of the front of the housing at an angle thatis typically tilted by around fifteen to about twenty-two degrees withrespect to the handle of the housing, for ergonomic reasons. In order tototally eliminate all internal flexible wiring and secondary PCBs, asingle PCB must extend from a bottom of the handle (where an interfacecable is connected) to a top of the housing (where success indicatorLEDs for the human interface reside for visibility). The fifteen totwenty-two degree tilt of the handle forces this single PCB to be tiltedby this same angle with respect to the imaging axis of the imaging lensassembly, thereby requiring that the known imaging lens system be placedon a secondary PCB tilted by that angle with respect to the main PCB.Multiple PCBs decrease reliability.

The market for handheld area readers is growing, but market growth ishampered not only by the relatively high cost of the scan engines, asdriven by their complex electro-mechanical structure that employsmultiple PCBs and/or ribbon cable interconnects and/or multipleconnectors, alignment fixtures, etc, but also by performance issues,such as a limited working distance range due to pixel resolutionconstraints and depth of focus constraints, as well as by parallaxissues. Accordingly, there is a need to provide a compact, low cost,high performance, and durable scan engine and an apparatus for, and amethod of, electro-optically reading a target by image capture employingthe compact scan engine in a handheld reader that would spur marketgrowth.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, together with the detailed description below, are incorporated inand form part of the specification, and serve to further illustrateembodiments of concepts that include the claimed invention, and explainvarious principles and advantages of those embodiments.

FIG. 1 is a side view of a handheld area reader for electro-opticallyreading targets by image capture in accordance with this disclosure.

FIG. 2 is a sectional view of the reader of FIG. 1, showing oneembodiment of internal components mounted on a single PCB.

FIG. 3 is an exploded view of the internal components of FIG. 2, as seenfrom a rear side of the PCB.

FIG. 4 is an exploded view of the internal components of FIG. 2, as seenfrom a front side of the PCB.

FIG. 5 is an enlarged broken-away view analogous to FIG. 2, showing thefolded path of the imaging field of view.

FIG. 6 is an enlarged broken-away view analogous to FIG. 2, showing thefolded path of the aiming light.

FIG. 7 is a top plan view diagrammatically depicting the size andlocation of the imaging field of view at the front end of the reader ofFIG. 1.

FIG. 8 is a top plan view analogous to FIG. 7 for a reader according tothe prior art.

FIG. 9 is a top plan view diagrammatically depicting the size andlocation of the imaging field of view at a far end of a working distancerange for the reader of FIG. 1.

FIG. 10 is a top plan view analogous to FIG. 9 for a reader according tothe prior art.

FIG. 11 is an enlarged sectional view of a detail of the reader of FIG.2, showing another embodiment of internal components mounted on a singlePCB.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present invention.

The apparatus and method components have been represented whereappropriate by conventional symbols in the drawings, showing only thosespecific details that are pertinent to understanding the embodiments ofthe present invention so as not to obscure the disclosure with detailsthat will be readily apparent to those of ordinary skill in the arthaving the benefit of the description herein.

DETAILED DESCRIPTION

One aspect of this disclosure relates to a compact scan engine forelectro-optically imaging a target. The scan engine includes a singleprinted circuit board (PCB) tilted at an acute angle of inclinationrelative to the vertical and having a tilted front surface that facesthe target during imaging, and a tilted rear surface that faces awayfrom the target during imaging. The PCB also has an aperture thatextends through the PCB between the tilted front and rear surfaces. Asolid-state image sensor is mounted on the tilted rear surface and has atwo-dimensional sensor array with a field of view. An optical assembly,including a pair of fold mirrors, is mounted on the tilted rear surface.The fold mirrors are arranged relative to each other and relative to theimage sensor, for receiving return light returning from the target andpassing through the aperture along the horizontal, and for directing thereturn light along a folded optical path. An imaging lens assembly ismounted in the folded optical path between the fold mirrors and has animaging axis that is generally parallel to the PCB, and is operative forprojecting the return light onto the image sensor to enable the imagesensor to detect the return light over the field of view, and togenerate an electrical signal indicative of the detected return light.The imaging lens assembly

In accordance with another aspect of this disclosure, the scan engine ismounted in a handheld reader for electro-optically reading the target.The reader includes a housing having a front end, a light-transmissivewindow supported at the front end, and a handle for holding the housingin a handheld mode of operation. The PCB is mounted in the handle, bothof which are tilted at the same acute angle of inclination relative tothe vertical. The return light returning from the target passes throughthe window along an internal folded optical path that extends betweenthe window and the image sensor in the scan engine. The imaging lensassembly is mounted in the folded optical path between the fold mirrorsin the scan engine, and the imaging axis of the imaging lens assembly isgenerally parallel to the PCB in the scan engine. A controller is alsomounted on the PCB and is operatively connected to, and controlsoperation of, the scan engine, for processing the electrical signal intodata indicative of the target being imaged.

In accordance with still another aspect of this disclosure, a method ofelectro-optically reading a target by image capture is performed bysupporting a light-transmissive window at a front end of a housing,holding the housing in a handheld mode of operation with a handle tiltedat an acute angle of inclination relative to the vertical, mounting asingle printed circuit board (PCB) in the handle, tilting the PCB at thesame angle of inclination, the PCB having a tilted front surface thatfaces the target during imaging, and a tilted rear surface that facesaway from the target during imaging, forming an aperture to extendthrough the PCB between the tilted front and rear surfaces, mounting asolid-state image sensor having a two-dimensional sensor array with afield of view on the tilted rear surface, receiving return lightreturning from the target through the window and passing through theaperture along the horizontal, directing the return light along aninternal folded optical path by mounting a pair of fold mirrors on thetilted rear surface, projecting the return light onto the image sensorby mounting an imaging lens assembly having an imaging axis in theinternal folded optical path between the fold mirrors, and bypositioning the imaging axis to lie generally parallel to the PCB, toenable the image sensor to detect the return light over the field ofview, and to generate an electrical signal indicative of the detectedreturn light, and processing the electrical signal into data indicativeof the target being imaged.

Turning now to the drawings, reference numeral 10 in FIG. 1 generallyidentifies an exemplary ergonomic handheld imaging reader configured asa gun-shaped housing having an upper barrel or body 12 and a lowerhandle 14 tilted rearwardly away from the body 12 at an acute angle ofinclination, for example, an angle somewhere between twenty-two andfifteen degrees (as shown, fifteen degrees), relative to the vertical. Awindow 32 (see FIG. 2) is located adjacent the front or nose 16 of thebody 12 and is preferably also tilted relative to the vertical. Theimaging reader 10 is held in an operator's hand by the handle 14 andused in a handheld mode in which a trigger 18 is manually depressed toinitiate imaging of targets to be read in a range of working distancesrelative to the nose 16. The targets include symbol targets, such asone- and two-dimensional bar code symbols, as well as non-symbol targetsor forms, such as documents, labels, receipts, signatures, drivers'licenses, employee badges, and payment/loyalty cards, each bearingalphanumeric characters. The illustrated gun-shaped housing can also besupported in a stand or cradle in a hands-free mode of operation.Housings of other configurations can also be employed.

As shown in FIGS. 2-5, the reader 10 includes a scan engine having asingle printed circuit board (PCB) 20 mounted in the handle 14 andtilted at the same acute angle of inclination, e.g., fifteen degrees.The PCB 20 has a tilted front surface 22 (see FIG. 4) that faces thetarget and the window 32 during imaging, and a tilted rear surface 24(see FIG. 3) that faces away from the window 32 and away from the targetduring imaging. The PCB 20 has an aperture 26, preferably, but notnecessarily, generally rectangular, that extends entirely through thePCB 20 between the tilted front and rear surfaces 22, 24. As describedbelow, return light scattered and/or reflected from the target entersthe reader 10 through the window 32 and through the aperture 26 alongthe horizontal.

The scan engine also has a solid-state image sensor 28, for example, aCCD or a CMOS device having an area or two-dimensional sensor array ofaddressable image sensors or pixels lying in a plane and looking outover a field of view, and being rearwardly mounted on the tilted rearsurface 24. As explained in detail below, this is in contrast with priorart configurations where the image sensor 28 is frontwardly mounted on aPCB and faces forwardly toward the window and the target.

The scan engine also has an imaging lens assembly 30 consisting of aplurality of imaging lenses arranged along an imaging axis in a tubularholder. The imaging lens assembly 30 is operative for capturing andprojecting return light returning from the target, as described below,onto the image sensor 28.

The scan engine also has an optical assembly mounted on the tilted rearsurface 24, and operative for directing the return light passing throughthe window 32 and through the aperture 26 along a folded path. Theoptical assembly includes a chassis 34 mounted on the tilted rearsurface 24, and a pair of planar fold mirrors 36, 38 mounted on thechassis 34 and operative for folding the return light twice along thefolded path. Fold mirror 36 is juxtaposed with the aperture 26 and foldsthe return light passing along the horizontal through the aperture 36generally downwardly to the fold mirror 38. The fold mirror 38 isjuxtaposed with the imaging lens assembly 30 and is operative forfolding the return light from the fold mirror 36 to the imaging lensassembly 30. The fold mirrors 36, 38 are arranged relative to each otherat an obtuse angle of about 97.5 degrees. This allows the return lightto pass through the window 32 and the aperture 26 along the horizontal,whereupon the double-folded path allows the return light to pass alongthe imaging axis of the imaging lens assembly in a direction generallyperpendicular to the image sensor 28, which is surface-mounted on thePCB 20 that, as noted above, is tilted at fifteen degrees. Rather thanusing two fold mirrors, a triangular prism could be employed.

As previously noted, the image sensor in the prior art handheld readeris typically forwardly-facing and is positioned about 2.5 inches backfrom the nose 16 of the housing. This internal optical path length is arelatively short distance and causes the field of view to diverge over awide angle, e.g., on the order of forty degrees. One aspect of thisdisclosure is to deliberately position the image sensor 38 to face therear of the housing and to double-fold the internal optical path up andover the image sensor 28 using the two mirrors 36, 38. No other handheldreader points the image sensor 38 backwards and folds the internaloptical path like this. The result is that the internal optical pathlength has been approximately doubled to, e.g., about five inches andmore. The internal optical path length can be adjusted by mounting theimaging lens assembly 30 anywhere along the internal optical pathbetween the image sensor 28 and the window 32. In the exemplaryembodiment depicted in FIG. 11 and described in detail below, theimaging lens assembly 30 is mounted between the two fold mirrors 36, 38.

With the internal path length so doubled and lengthened, the field ofview angle can be halved while still achieving the required 1.75 inchfield of view width near the nose 16 of the housing. Thus, withreference to FIGS. 7 and 8, the reader 10 (FIG. 7) and its field of viewadjacent the nose 16 is compared with that of a prior art reader (FIG.8). A 100% Universal Product Code (UPC) symbol having a length of about1.75 inches will be entirely covered at the nose 16 of the reader 10,whereas, by contrast, that same symbol will only be covered at adistance of about 0.75 inches away from the nose of a prior art reader.The reader 10 thus has a wider field of view adjacent the nose 16.

With half the field of view angle, the size of the target image on theimage sensor 28 only decreases at half of the rate as the target ismoved away from the nose 16, with the result that the distance from theimaging lens assembly 30 can be doubled before the pixel resolutiondrops too low to read a target with elements of a given size. Withreference to FIGS. 9 and 10, the reader 10 (FIG. 9) and its field ofview (about twenty-eight degrees) far from the nose 16 is compared withthat of a prior art reader (FIG. 10) and its field of view (about fortydegrees). The narrower field of view of the reader 10 allows for moreconcentrated illumination light to be available at the far end of theworking distance range. As discussed above, the pixel resolution limitis pushed out further from the nose 16. Also, the field of view of thereader 10 at the far end of the working distance range is notinconveniently large.

In addition, since the internal optical path is longer than that whichhas been used in prior art readers, the depth of focus has thereforebeen increased, and the point of best focus can be moved further awayfrom the nose 16 of the housing while still retaining adequate imagesharpness near the nose 16 to read targets placed close to the nose 16.In other words, a doubling of the internal optical path length resultsin more than doubling the distance between the imaging lens assembly 30and the point of best focus, thereby providing a very significantincrease in overall depth of focus. When this increased depth of focusis combined with the extended pixel resolution described above, theoverall working range of the reader of this disclosure becomesdramatically increased, as compared to imaging readers of conventionaldesign.

As best seen in FIG. 6, the scan engine also has an aiming lightassembly also mounted in the housing and operative for projecting anaiming light pattern or mark, such as a “crosshair” pattern, byemploying an aiming light source 40, e.g., an aiming laser or LED, alsomounted on the rear surface 24 of the PCB 20, for emitting an aiminglight beam through an aiming lens 42 supported by the chassis 34 foroptically modifying the aiming light beam, to the same pair of foldmirrors 38, 36 for twice folding the aiming light beam prior to passingthrough the aperture 26 and the window 32 to the target. The user aimsthe aiming pattern on the target to be imaged, prior to reading. Byemploying the same pair of fold mirrors 38, 36 for the return light andfor the aiming beam, the above-described parallax issue is minimized.

The twice-folded aiming light beam increases the distance between theaiming light assembly and a target positioned out in front of the nose16. This increased optical path length allows a reduction in theabove-described parallax issue between the imaging field of view and theaiming light beam. With the extended optical path created by thetwice-folded aiming light beam, the angular parallax is reduced, so thatthe aiming light beam remains well centered within the field of view ofthe image sensor 28 over a range that is larger than any other imagingreader.

In order to take full advantage of the extended depth of focus andextended pixel resolution of this disclosure, the scan engine alsopreferably has an illuminating light assembly also mounted in thehousing of the imaging reader and preferably including a plurality ofilluminating light sources, e.g., light emitting diodes (LEDs) 44 andilluminating lenses 46 arranged to uniformly illuminate the target withillumination light. If ambient illumination is too dim, the reader maynot be able to decode a symbol target, or clearly image a non-symboltarget, all the way out to the point where either the pixel resolutionor the depth of focus runs out of range. The result would be failure totake maximum advantage of this disclosure. Hence, the illumination LEDs44 are mounted on the front surface 22 (see FIG. 4) of the PCB 20, andshine directly out through the window 32. This places the illuminationLEDs 44 a couple of inches closer to the target than the image sensor28, thereby providing more intense illumination on the target.

In prior art readers, where a wide field of view angle is required, forreasons described above, the illuminating light assembly must project awide cone of light to illuminate the entire field of view. Spreading thelight over a wide area diminishes the intensity of the illuminationlight in any given portion of the field of view. In accordance with thisdisclosure, however, since the field of view angle is narrower thanheretofore, the illuminating lenses 46 on the illumination LEDs 44 canbe designed to project a much narrower angle of illumination, therebyincreasing the intensity of the illumination light.

In further accordance with this disclosure, the illuminated area isblocked where it would extend beyond the edge of the imaging field ofview by an internal chamber 48 mounted on the front surface 22 of thePCB 20 and extending from the PCB 20 to the window 32. The result is theprojection of a bright rectangle of illumination light that correspondsquite closely with the actual imaging field of view. This supplementsthe aiming light assembly described above. The aiming light assembly canbe used to designate a particular target positioned within the field ofview, while the sharply cut off illumination helps a user see where theinvisible field of view ends, thus avoiding failure to scan due to aportion of the target being positioned outside the field of view. Thesharply cut-off illumination also masks the bright illumination from theeyes of people in the vicinity of the reader, thus avoiding one of thedisadvantages of imager sensors, whose very bright illumination can beannoying to users and people nearby.

As previously described, the trigger 18 is manually depressed toinitiate imaging of targets to be read in the handheld mode ofoperation. Sometimes, as best seen in FIG. 4, the scan engine mayoptionally be provided with an object sensing assembly mounted on thefront surface 22 and operative for sensing the target in the field ofview through the window 32 in a hands-free mode of operation. The objectsensing assembly includes an infrared emitter 52 and an infrareddetector 56 spaced apart from each other on the PCB 20 within thechamber 48, and a pair of object lenses 54, 58, one for each infraredemitter 52 and detector 56.

The image sensor 28, the illuminating LEDs 44 of the illuminatingassembly, the aiming light source 40 of the aiming light assembly, andthe optional infrared emitter 52 and infrared detector 56 areoperatively connected to a controller or programmed microprocessor 50operative for controlling the operation of these components. Preferably,the microprocessor 50 is the same as the one used for decoding returnlight scattered from a symbol target and/or for processing the capturedtarget images.

In operation, the microprocessor 50 sends command signals to energizethe aiming light source 40 to project the aiming light pattern on thetarget, to energize the illuminating LEDs 44 for a short time period,say 500 microseconds or less to illuminate the target, and also toenergize the image sensor 28 to collect light from the target onlyduring said time period. A typical array needs about 16 to 33milliseconds to acquire the entire target image and operates at a framerate of about 30 to 60 frames per second. The array may have on theorder of one million addressable image sensors.

As best seen in FIG. 11, the above-described imaging lens assembly 30preferably consists of a Cooke triplet having lenses 60, 62, 64 spacedapart along an imaging axis 68, or in close proximity with one another,and mounted in a tubular cylindrical holder 66. The imaging lensassembly 30 could also be a doublet. Other lenses could be added. Anaperture stop could also be positioned between any two adjacent lenses.The imaging lens assembly 30 is mounted in the internal folded pathbetween the above-described fold mirrors 36, 38. The imaging axis 68 ispositioned to be generally parallel, and close, to the tilted PCB 20.This is in contrast with the above-described embodiment where theimaging axis 68 is positioned to be generally perpendicular to thetilted PCB 20. The generally parallel, and close, positioning of theimaging axis 68 relative to the tilted PCB 20 renders the scan engine ofFIG. 11 more compact than in the previous embodiment.

In the foregoing specification, specific embodiments have beendescribed. However, one of ordinary skill in the art appreciates thatvarious modifications and changes can be made without departing from thescope of the invention as set forth in the claims below. Accordingly,the specification and figures are to be regarded in an illustrativerather than a restrictive sense, and all such modifications are intendedto be included within the scope of present teachings.

The benefits, advantages, solutions to problems, and any element(s) thatmay cause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeatures or elements of any or all the claims. The invention is definedsolely by the appended claims including any amendments made during thependency of this application and all equivalents of those claims asissued.

Moreover in this document, relational terms such as first and second,top and bottom, and the like may be used solely to distinguish oneentity or action from another entity or action without necessarilyrequiring or implying any actual such relationship or order between suchentities or actions. The terms “comprises,” “comprising,” “has,”“having,” “includes,” “including,” “contains,” “containing,” or anyother variation thereof, are intended to cover a non-exclusiveinclusion, such that a process, method, article, or apparatus thatcomprises, has, includes, contains a list of elements does not includeonly those elements, but may include other elements not expressly listedor inherent to such process, method, article, or apparatus. An elementproceeded by “comprises . . . a,” “has . . . a,” “includes . . . a,” or“contains . . . a,” does not, without more constraints, preclude theexistence of additional identical elements in the process, method,article, or apparatus that comprises, has, includes, or contains theelement. The terms “a” and “an” are defined as one or more unlessexplicitly stated otherwise herein. The terms “substantially,”“essentially,” “approximately,” “about,” or any other version thereof,are defined as being close to as understood by one of ordinary skill inthe art, and in one non-limiting embodiment the term is defined to bewithin 10%, in another embodiment within 5%, in another embodimentwithin 1%, and in another embodiment within 0.5%. The term “coupled” asused herein is defined as connected, although not necessarily directlyand not necessarily mechanically. A device or structure that is“configured” in a certain way is configured in at least that way, butmay also be configured in ways that are not listed.

It will be appreciated that some embodiments may be comprised of one ormore generic or specialized processors (or “processing devices”) such asmicroprocessors, digital signal processors, customized processors, andfield programmable gate arrays (FPGAs), and unique stored programinstructions (including both software and firmware) that control the oneor more processors to implement, in conjunction with certainnon-processor circuits, some, most, or all of the functions of themethod and/or apparatus described herein. Alternatively, some or allfunctions could be implemented by a state machine that has no storedprogram instructions, or in one or more application specific integratedcircuits (ASICs), in which each function or some combinations of certainof the functions are implemented as custom logic. Of course, acombination of the two approaches could be used.

Moreover, an embodiment can be implemented as a computer-readablestorage medium having computer readable code stored thereon forprogramming a computer (e.g., comprising a processor) to perform amethod as described and claimed herein. Examples of suchcomputer-readable storage mediums include, but are not limited to, ahard disk, a CD-ROM, an optical storage device, a magnetic storagedevice, a ROM (Read Only Memory), a PROM (Programmable Read OnlyMemory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM(Electrically Erasable Programmable Read Only Memory) and a Flashmemory. Further, it is expected that one of ordinary skill,notwithstanding possibly significant effort and many design choicesmotivated by, for example, available time, current technology, andeconomic considerations, when guided by the concepts and principlesdisclosed herein, will be readily capable of generating such softwareinstructions and programs and ICs with minimal experimentation.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus, the following claimsare hereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

1. A compact scan engine for electro-optically imaging a target,comprising: a single printed circuit board (PCB) tilted at an acuteangle of inclination relative to the vertical, the PCB having a tiltedfront surface that faces the target during imaging, and a tilted rearsurface that faces away from the target during imaging, the PCB havingan aperture that extends through the PCB between the tilted front andrear surfaces; a solid-state image sensor mounted on the tilted rearsurface and having a two-dimensional sensor array with a field of view;an optical assembly on the tilted rear surface and including a pair offold mirrors arranged relative to each other and relative to the imagesensor, for receiving return light returning from the target and passingthrough the aperture along the horizontal, and for directing the returnlight along a folded path; and an imaging lens assembly mounted in thefolded path between the fold mirrors and having an imaging axis thatextends generally parallel to the PCB, for projecting the return lightonto the image sensor to enable the image sensor to detect the returnlight over the field of view, and to generate an electrical signalindicative of the detected return light.
 2. The scan engine of claim 1,wherein the optical assembly includes a chassis mounted on the tiltedrear surface, and wherein the fold mirrors and the imaging lens assemblyare mounted on the chassis and are operative for folding the returnlight twice along the folded path, one of the fold mirrors beingoperative for folding the return light passing through the aperturethrough the imaging lens assembly to the other of the fold mirrors, andthe other of the fold mirrors being operative for folding the returnlight from the imaging lens assembly to the image sensor.
 3. The scanengine of claim 2, wherein each fold mirror is planar, and wherein thechassis holds the planar fold mirrors at an obtuse angle relative toeach other.
 4. The scan engine of claim 2, wherein the imaging lensassembly includes a plurality of imaging lenses arranged along theimaging axis.
 5. The scan engine of claim 2, and an aiming lightassembly mounted on the tilted rear surface, for directing an aimingpattern onto the same fold mirrors, and for projecting the aimingpattern on the target, wherein the aiming light assembly includes anaiming light emitting diode (LED) mounted on the tilted rear surface andoperative for emitting an aiming light beam through an aiming lenssupported by the chassis for optically modifying the aiming light beam,and to the same pair of fold mirrors, for twice folding the aiming lightbeam prior to passing through the aperture to the target.
 6. A readerfor electro-optically reading a target, comprising: a housing having afront end, a light-transmissive window supported at the front end, and ahandle for holding the housing in a handheld mode of operation, thehandle being tilted at an acute angle of inclination relative to thevertical; a compact scan engine for imaging the target, the scan engineincluding a single printed circuit board (PCB) mounted in the handle andtilted at the same acute angle of inclination, the PCB having a tiltedfront surface that faces the target during imaging, and a tilted rearsurface that faces away from the target during imaging, the PCB havingan aperture that extends through the PCB between the tilted front andrear surfaces, a solid-state image sensor mounted on the tilted rearsurface and having a two-dimensional sensor array with a field of view,an optical assembly having a pair of fold mirrors mounted on the tiltedrear surface for receiving return light returning from the targetthrough the window and passing through the aperture along thehorizontal, and for directing the return light along an internal foldedpath between the window and the image sensor, and an imaging lensassembly mounted in the internal folded path between the fold mirrorsand having an imaging axis that extends generally parallel to the PCB,and operative for projecting the return light onto the image sensor toenable the image sensor to detect the return light over the field ofview, and to generate an electrical signal indicative of the detectedreturn light; and a controller mounted on the PCB and operativelyconnected to, and controlling operation of, the scan engine, forprocessing the electrical signal into data indicative of the targetbeing imaged.
 7. The reader of claim 6, wherein the optical assemblyincludes a chassis mounted on the tilted rear surface, and wherein thefold mirrors and the imaging lens assembly are mounted on the chassisand are operative for folding the return light twice along the internalfolded path, one of the fold mirrors being operative for folding thereturn light passing through the window and the aperture through theimaging lens assembly and to the other of the fold mirrors, and theother of the fold mirrors being operative for folding the return lightfrom the imaging lens assembly to the image sensor.
 8. The reader ofclaim 7, wherein each fold mirror is planar, and wherein the chassisholds the planar fold mirrors at an obtuse angle relative to each other.9. The reader of claim 7, wherein the imaging lens assembly includes aplurality of imaging lenses arranged along the imaging axis.
 10. Thereader of claim 7, and an aiming light assembly for projecting an aimingpattern on the target, the aiming light assembly including an aiminglight emitting diode (LED) mounted on the tilted rear surface andoperative for emitting an aiming light beam through an aiming lenssupported by the chassis for optically modifying the aiming light beam,and to the same pair of fold mirrors, for twice folding the aiming lightbeam prior to passing through the aperture and the window to the target.11. The reader of claim 6, and a light chamber mounted on the tiltedfront surface and extending between the PCB and the window.
 12. Thereader of claim 6, wherein the acute angle of inclination is from aboutfifteen degrees to about twenty-two degrees.
 13. The reader of claim 6,and a trigger mounted on the handle, for manually actuating reading. 14.A method of electro-optically reading a target, comprising: supporting alight-transmissive window at a front end of a housing; holding thehousing in a handheld mode of operation with a handle tilted at an acuteangle of inclination relative to the vertical; mounting a single printedcircuit board (PCB) in the handle and tilting the PCB at the same angleof inclination, the PCB having a tilted front surface that faces thetarget during imaging, and a tilted rear surface that faces away fromthe target during imaging; forming an aperture to extend through the PCBbetween the tilted front and rear surfaces; mounting a solid-state imagesensor having a two-dimensional sensor array with a field of view on thetilted rear surface; receiving return light returning from the targetthrough the window and passing through the aperture along thehorizontal, and directing the return light along an internal folded pathbetween the window and the image sensor by mounting a pair of foldmirrors on the tilted rear surface; projecting the return light onto theimage sensor by mounting an imaging lens assembly in the internal foldedpath between the fold mirrors, and by positioning an imaging axis of theimaging lens assembly to extend generally parallel to the PCB, to enablethe image sensor to detect the return light over the field of view, andto generate an electrical signal indicative of the detected returnlight; and processing the electrical signal into data indicative of thetarget being imaged.
 15. The method of claim 14, and mounting the foldmirrors and the imaging lens assembly on a chassis mounted on the tiltedrear surface.
 16. The method of claim 14, and orienting the fold mirrorsat an obtuse angle relative to each other.
 17. The method of claim 14,and configuring the imaging lens assembly with a plurality of lensesthat extend along the imaging axis.
 18. The method of claim 14, andorienting the fold mirrors and the imaging lens assembly relative toeach other and relative to the image sensor so that the return lightpasses through the window and the aperture along the horizontal.
 19. Themethod of claim 15, and projecting an aiming pattern on the target withan aiming light emitting diode (LED) mounted on the tilted rear surfaceto emit an aiming light beam to the same pair of fold mirrors for twicefolding the aiming light beam prior to passing through the aperture andthe window to the target.
 20. The method of claim 14, and mounting alight chamber on the tilted front surface between the PCB and thewindow.